Array of diffraction limited lasers and method of aligning same

Abstract

A one-dimensional semiconductor laser array assembly typically comprising a one-dimensional semiconductor laser array, a heatsink upon which the laser array is bonded, and a lens assembly. The one-dimensional semiconductor laser array consists of a plurality of emitters with each emitter electrically connected in parallel to a power supply. The bonding agent, typically silver epoxy, must be of a uniform thickness so that the laser array is aligned properly upon the heatsink. The lens assembly is typically comprised of a refractive lens, typically of a bi-convex design, and a one-dimensional array of binary optical elements. The one-dimensional array of binary optical elements is designed such that each element has a front surface having a binary optic diffractive element etched thereon. The refractive lens and the one-dimensional array of binary optical elements are aligned and held in place by means of ears protruding from the heatsink. There is also provided by this invention a two-dimensional semiconductor laser array assembly consisting of a plurality of one-dimensional semiconductor laser array assemblies positioned substantially parallel to one another, within a clamping fixture, with the lens assembly of each one-dimensional laser array assembly positioned such that the output of each one-dimensional laser array is focused to the same point in the far field to provide a high intensity output and method for so aligning the two-dimensional laser array assembly. A lens assembly is also provided for focusing the output at a variable point.

I claim: 
     
       1. A one-dimensional semiconductor laser array assembly, comprising: a) a one-dimensional semiconductor laser array having a plurality of emitters wherein each emitter is electrically connected to a power supply means;   b) a heatsink means for absorbing heat from the semiconductor laser array;   c) a bonding means for attaching the semiconductor laser array to the heatsink means and transferring heat from the semiconductor laser array to the heatsink means, the bonding means having a uniform thickness;   d) a refractive lens means for collimating a fast axis of the output of each emitter of the semiconductor laser array; and   e) a one-dimensional array of binary optical elements for collimating a slow axis of the output of the emitters of the semiconductor laser array and correcting aberrations therein, wherein each individual binary optical element corresponds to a distinct individual emitter of the semiconductor laser array, each binary optical element comprising a substantially planar substrate having a front surface wherein the front surface has been formed such that the optical path length travelled by each ray of divergent light emitted by an emitter of the semiconductor laser array is equal upon the ray's exit from the front surface of the binary optical element.   
     
     
       2. A one-dimensional semiconductor laser array assembly, as recited in claim 1, wherein the front surface of each binary optical element has a binary optic diffractive element etched thereon. 
     
     
       3. A one-dimensional semiconductor laser array assembly, as recited in claim 2, wherein the bonding means is comprised of silver epoxy. 
     
     
       4. A one-dimensional semiconductor laser array assembly, as recited in claim 3, wherein the refractive lens means is a biconvex rod lens. 
     
     
       5. A one-dimensional semiconductor laser array assembly, as recited in claim 3, wherein the heatsink means is comprised of a material selected from the group consisting of beryllium oxide (BeO) and Elkonite (Cu-W). 
     
     
       6. A one-dimensional semiconductor laser array assembly, as recited in claim 3, wherein the binary optic diffractive element is a structure selected from the group consisting of a two-phase level structure, a four-phase level structure, an eight-phase level structure, and a sixteen-phase level structure. 
     
     
       7. A one-dimensional semiconductor laser array assembly, as recited in claim 3, wherein the heatsink means comprises a holding means for fixedly retaining the refractive lens means and the binary optic diffractive element. 
     
     
       8. A one-dimensional semiconductor laser array, as recited in claim 3, further comprising at least one lens positioned to focus the collimated output of the emitters. 
     
     
       9. A one-dimensional semiconductor laser array, as recited in claim 8, wherein two plano convex lenses of equal focal length are adjustly positioned to focus the collimated output of the emitters at a variable position. 
     
     
       10. A one-dimensional semiconductor laser array, as recited in claim 9, wherein two fixed lenses are positioned between the two plano convex lenses to prevent the collimated output of the emitter from being focused to a spot between the two plano convex lenses. 
     
     
       11. A two-dimensional semiconductor laser array assembly, comprising: a) a plurality of one-dimensional semiconductor laser array assemblies wherein each one-dimensional semiconductor laser array assembly comprises: 1) a one-dimensional semiconductor laser array having a plurality of emitters wherein each emitter is electrically connected to a power supply means;   2) a heatsink means for absorbing heat from the semiconductor laser array;   3) a bonding means for attaching the semiconductor laser array to the heatsink means and transferring heat from the semiconductor laser array to the heatsink means, the bonding means having a uniform thickness;   4) a refractive lens means for collimating a fast axis of the output of each emitter of the semiconductor laser array; and   5) a one-dimensional array of binary optical elements for collimating a slow axis of the output of the emitters of the semiconductor laser array and correcting aberrations therein, wherein each individual binary optical element corresponds to a distinct individual emitter of the semiconductor laser array, each binary optical element comprising a substantially planar substrate having a front surface wherein the front surface has been formed such that the optical path length travelled by each ray of divergent light emitted by an emitter of the semiconductor laser array is equal upon the ray's exit from the front surface of the binary optical element; and     b) a clamping fixture for fixedly retaining the plurality of one-dimensional semiconductor laser array assemblies such the plurality of one-dimensional semiconductor laser array assemblies are substantially parallel.   
     
     
       12. A two-dimensional semiconductor laser array assembly, as recited in claim 11, wherein the front surface of each binary optical element has a binary optic diffractive element etched thereon. 
     
     
       13. A two-dimensional semiconductor laser array assembly, as recited in claim 12, wherein each bonding means is comprised of silver epoxy. 
     
     
       14. A two-dimensional semiconductor laser array assembly, as recited in claim 13, wherein each refractive lens means is a biconvex rod lens. 
     
     
       15. A two-dimensional semiconductor laser array assembly, as recited in claim 13, wherein each heatsink means is comprised of a material selected from the group consisting of beryllium oxide (BeO) and Elkonite (Cu-W). 
     
     
       16. A two-dimensional semiconductor laser array assembly, as recited in claim 13, wherein each binary optic diffractive element is a structure selected from the group consisting of a two-phase level structure, a four-phase level structure, an eight-phase level structure, and a sixteen-phase level structure. 
     
     
       17. A two-dimensional semiconductor laser array assembly, as recited in claim 13, wherein each heatsink means comprises a holding means for fixedly retaining the refractive lens means and the binary optic diffractive element. 
     
     
       18. A two-dimensional semiconductor laser array, as recited in claim 13, further comprising at least one lens positioned to focus the collimated output of the emitters. 
     
     
       19. A two-dimensional semiconductor laser array, as recited in claim 18, wherein two plano convex lenses of equal focal length are adjustly positioned to focus the collimated output of the emitters at a variable position. 
     
     
       20. A two-dimensional semiconductor laser array, as recited in claim 19, wherein two fixed lenses are positioned between the two plano convex lenses to prevent the collimated output of the emitter from being focused to a spot between the two plano convex lenses. 
     
     
       21. A method for aligning the output of a two-dimensional semiconductor laser array assembly, comprising the steps of: a) placing a first one-dimensional semiconductor laser array assembly in a clamping fixture;   b) placing a second one-dimensional semiconductor laser array assembly in the clamping fixture such the second one-dimensional semiconductor laser array assembly is substantially parallel to the first one-dimensional semiconductor laser array assembly;   c) positioning a set of collimating optics for the second one-dimensional semiconductor laser array assembly such that the output of the second semiconductor laser array, placed within the clamping fixture, travels through substantially the center of the collimating optics;   d) supplying power to each of the one-dimensional semiconductor laser array assemblies following the positioning of the collimating optics;   e) introducing a transform lens in the optical path of the output of each one-dimensional semiconductor laser array assembly to simulate a far field of the two-dimensional semiconductor laser array assembly;   f) monitoring the power level at the focal point of the transform lens;   g) altering the position of the collimating optics until a maximum power level is detected by the monitor;   h) retaining the collimating optics in the position corresponding to the highest power level detected; and   i) repeating steps (b) through (h) for each additional one-dimensional semiconductor laser array assembly of the two-dimensional semiconductor laser array assembly.